Cathode-ray apparatus



`lume 8, 1948. D, R, DE TAR cATHoDE RAY PPARATUS Filed July 250, 1945 Invenbof. Donald R DeTar,

His Attorne.

Patented IJune 8, 1948 CAT-{DE-RAY APPARATUS Donald R. De Tar, Stratford, Conn., assigner to General Electric Company, a corporation of New York Application .lilly 30, 1945, Serial No. 607,786

Claims. l

This invention relates to cathode ray apparatus and particularly to Idevices for focusing and for centering the cathode ray beam in electron discharge devices of the cathode ray type.

Cathode ray tubes such as those employed in television apparatus are commonly provided with a so-called electron gun for producing a cathode ray beam and for projecting the beam onto a luminescent screen. A device is provided for concentrating or focusing the beam and may take the form of a coil wound about the neck of the cathode ray tube between the point of origin of the beam and the deflecting members which are provided to direct the beam to selected portions of the screen. It is also ldesirable to provide a device for centering the beam, so that it strikes the fluorescent screen at a predetermined desired point whenever the deecting members are not energized. Centering may be accomplished in a cathode ray tube having magnetic deecting coils by providing a direct current circuit for the horilzontal and vertical deflecting coils so that the direct current flowing through these coils may be adjusted, thereby adjusting the position of the beam. In some types of cathode ray apparatus, however, the deflecting members are required to rotate about the envelope of the cathode ray tube and the adjustment or centering of the beam by varying the direct current in the deflecting coils is no longer possible. In such apparatus it has been the practice to mount the focusing coil so that its axis may be tilted or to provide an additional magnetic member or set of coils arranged about the neck of the tube ahead of the focusing coil. This latter arrangement, however, requires that the tube have a substantially longer neck portion. Cathode ray tubes are employed in viewing apparatus of the projection type such as those employing the system known as the Schmidt optical system wherein the image is projected from a curved mirror in front of the screen back along the outside of the envelope parallel to the tube axis. ln these projection systems it is desirable that the tube be as short as possible and of as small a diameter as possible, whereas both the tilted coil and additional centering devices require extra space. Accordingly, it is an object of this invention to provide a focusing and centering unit for cathode ray electron dis- 'charge devices which shall occupy a minimum space.

It is another object of the invention to provide a simple and eifective focusing and centering unit 'for cathode ray tubes having rotatable deflecting Cil struction and make possible the remote control of the focusing and Acentering functions.

The novel features which are believed to be characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing in which Fig. l represents a cathode ray tube in its supporting assembly and provided with a focusing and centering unit embodying this invention; Fig. 2 is a schematic diagram illustrating the arrangement of the elements of the tube and the control circuit for the focusing and centering unit; Fig. 3 is an enlarged longitudinal sectional View of the focusing and centering unit; and Fig. 4 is an exploded perspective view of a portion of the unit shown in Fig. 3.

Referring now to Fig. 1 of the drawing, a cathode ray tube I having a bowl portion 2 and a neck portion 3 is mounted in a supporting frame 4 which is secured to a supporting structure (not shown) by a plurality of arms a portion of one of which is indicated at 5. The illustrated arrangement for mounting a cathode ray tube is suitable for use in connection with an optical projection system of the Schmidt type, the supporting arms 5 of the mounting being made as thin and narrow as practicable and not more than three such arms being employed in order to offer a minimum obstruction to the light. The tube I is secured within the frame d by a suitable chucking mechanism 5 which engages the neck 3 of the tube near the bowl 2. At the end of the frame it is mounted a focusing and centering unit 1 embodying the invention, and the tube is located with respect to the unit 'I by a clamp B engaging the neck portion 3 and connected to the unit 'l through an adjustable optical focusing device Sl. When the tube is first placed ywithin its support, it is located in the approximate desired position and the clamp 3 is secured about the neck 3, the chuck 6 being arranged to permit longitudinal sliding movement of the tube therein. The tube is then focused with respect to the optical system by turning an adjusting collar l0 of the focusing device 9. 'The adjustment of this collar moves the tube longitudinally with respect to the supporting structure. The defiecting coil assembly H is provided for deflecting the cathode ray beam, and this asmembers which shall be of simple andrugged consembly is rotatably mounted within the frame t on ball bearings l2, the rotation being effected through a worm I3 and gear I4 driven in a rcquired manner by a suitable motor (not shown). Connections to the deecting coil are made through slip rings I5 and I6 which are engaged by stationary brushes (not shown). Because the deflecting coils are mounted in a, rotating structure, it is not possible to vary the direct current components of the deflecting coil current in orer to center the cathode ray beam and a separate centering device must be provided. For this purpose centering coils are included in thestructure of the unit 1, which also includes the focusing coil for concentrating or focusing the cathode ray beam.

Referring now to Fig. 2 the cathode ray tube I has been shown with a portion .of the neck- 3 broken away to include a diagrammatic illustration of the coils and control resistors for the focusing and centering unit 1, this unit, for purposes of illustration, being shown as turned at right angles to its actual position. The deflecting coil has been omitted from Fig." 2 to avoid complication of the gure. They cathoderay tube l is provided with suitable electrodes for producing a cathode ray beam and including a cathode I1, a first anodeA I8- andv a second anode I9. The` intensity `of the beam. iscontrolled by energizationof a control electrode or grid 29. In order to concentrate the beam and to focus it upon the luminescent screen, provided at theA end of the bowl portion 2 in accordance withcommon practice,I a focusing coil 2lv is provided in the unit 1'. The focusing coil comprising a large number `of turns about the neck 3 arranged on a suitable magnetic core to4 produce a focusing eld having lan axis in alignment with the longitudinal axis of the tube i. The intensityof the focusing field may bechangedbynadjustment of a variable resistor; 22 in theV direct current circuit of the coil 2|. Also included in the unit 1 is the set of vcentering coils comprising afirst centering coil 23' and a second centering coi-124, one half of each of the coils being arranged ondiametrically opposite sides of the neck 3- of the tube;v the coils 23 and 24 have axes at right angles to each other and to the axis of the tube. The intensity and direction of the centering eld produced by the' coils- 23 may be adjusted by operation of a potentiometer 25,'Y and thej intensity and direction of the` 'eld producedby the coil 24- may similarly be varied by adjustment of a potentiometer 26.

During the operation of the cathode ray tube shown in Figs. 1 and2, suitable potentials are applied tor the anodesl8 and t9 and a cathode ray beam is projected against the screen at the left-hand end of the tube. Thisfbeam is concentrated and focused on the screen byr adjustment of the rheostat 22 .tocontrolv the energization of the focusing coil 2l, and if the beam is not-in the required rcenter position it isrbrought into-such position. by suitable adfrustment of the potentiometers .25 and 26. Since the focusing and cen-tering unit 1- is xedwith respect tothe tube and its support, the control resistances1 22, 25 and 26may be located'. on a control boardremote from the cathode ray apparatus. TheA deflecting coil assembly I I' may their berotated to' provide deflections in any direction. i

As shown in` Figs'. 3 and 4, .the centering. coils 23T and 24 are`r mountedon. an insulating fornr 21 sothat the magnetic core structure of the focusing coil serves also as the` core structure for the centering. coils'. This magnetic ,core `structure comprises an inner cylindrical sleeve member 28 and an outer cylindrical sleeve member 29. The inner member is provided with an outwardly extending end flange 30 which engages the outer member 29, and the outer member is provided with an inwardly extending flange 3l at its opposite end. The inner member 28 is shorter than the outer member -29 andprovidesanannular air gap as indicated at 32. The focusing coil comprising a large number of turns is arranged within the hollow toroidal core structure formed by the members 28 and 29 as indicated at 33. This general type of focusing coil and core structure is Well known in the art and provides a concentrated magnetic .eld about the annular poles provided bythe magnetic structure on either side of the .air gap 32. The field thus produced tends to concentrate the cathode ray beam along the central longitudinal axis of the coil. The focusing coil is enclosed in inner and outer insulating` sheaths.` 34 and. 35 respectively and` is enclosed andsealedin aimetallic` container-36 which completely surrounds the coil, the leads for the coil indicated. at` 3-1 beingv broughtgout through. sealed connecting posts 38.

During theassembly of the unit 1,.the.centering coils` 23 and. 24 are wound onthe form 21 where they are located in suitablelongitudinal slots- 39 Amilled inthe form. Two of the slotsl are widened as indicated .at 4-and 4I to provide for theterminal connections tothe coils. 4After the coils havezbeen. wound on the form `21', a layer of suitable i'nsulatingmaterlal is..wound about the coils .over the. form as indicated fat .42. Outwardlly projectingseg'ments 43 are provided near the leftY end of theform 21. andy constitute an annular ring of stops which .engage the left end ofthe magnetic lcore..or cylinder. 28. when the centering coil assembly, is insertedin. the cylinder. Three. additional. outwardly. projecting. segments orlugs 44. areprovided, two of which are. shown, and. these=proiections extend through. notches 145, in the end ofptliecorelr and lock the coil form vagainst; rotationi-n thecore. Thefocusing. coil 33-in its metal container .361s thenplacedl over the core cylinder .29 withthe terminal posts vv3B extending through openings I6 in the ange-3. The corecylinder 28`.with the coils thereon `is then inserted', in the outer cylinder 29 with a notch 41,.shownin Eig. l4:, slipping over a punched out projection 482i shown-at the upper right-hand comer.- of Fig. 3. .After the core 28 is inposition in the core 29, itmay be rotated so that the projection 48 locks the cores together and prevents withdrawal of thecoil assembly. Thecores 28. and 29. maybe locked together in` anyvvsuitablemanner, for Venampleby punching in a portion ofthe core 29 to enter the notch 41 in its rotated4 position andprevent further rotation.

vIt will be. observed that the focusing. and'` centering coil unit- 1 provides `a compactstructure which may -be arranged. closely about lthe neck 3 and. will provide minimuminterferencewith the light rays f-rcnn-an` optical projection system, for example. Furthermorefby constructing. Athe oentering'coils inj a manner sof thatthey may utllize the same; magnetic .core structure as .the focusing coil, it is unnecessary to increase the lengthV of the-'tube neclcin-theusual manner to accommodate an additional coil assembly along the axis ofthe tube. Thestructure vof vthe unit 'l is simple and rugged; and when the core-281s locked; within. the corer 29 thecenteringfcoils are located -in--their required position bytheengae ment of the projections 43 and 413 with the end of the core 28 and the notches 45, and furthermore the ends of the coils 23 and 2d which are bent outwardly over th'e iiange 3l, after insertion in the core further serve to prevent movement of the centering coil to the left as shown in Fig. 3. The focusing coil is locked within the hollow toroidal core structure and cannot accidentally be removed or displaced with respect to the remaining parts of the unit.

While a particular embodiment of the invention has been described and illustrated, it will, of course, be understood that it is not desired to limit the invention thereto since dierent modifications will occur to those skilled in the art. It is therefore intended by the appended claims to cover all modifications which fall within the spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A cathode ray electron discharge device comprising an envelope, an electron gun for projecting a cathode ray beam in said envelope, a uorescent screen arranged in the path of the beam, a hollow annular magnetic .core closely surrounding said envelope, a focusing coil positioned within said core for concentrating said beam, and a pair of coils arranged between said core and said envelope on axes at right angles to each other and to the axis of said beam whereby the position of said beam may be changed by adjusting the excitation of the coils of said pair of coils.

2. A cathode ray electron discharge device comprising an envelope having a cylindrical neck portion, means arranged within said portion for projecting a cathode ray beam into the body portion of said envelope, a fluorescent screen arranged in the path of the beam, a focusing coil surrounding said neck portion for concentrating said beam, a hollow toroidal magnetic core surrounding said coil and having a portion thereof arranged between said coil and said envelope, and a pair of coils arranged between said portion of said core and said neck portion, said coils of said pair being arranged to produce magnetic fields at right angles to each other and to the axis of said beam whereby the position of the beam may be changed by adjusting the excitation of the coils of said pair of coils.

3. A combined focusing and centering coil -assembly for a cathode ray tube comprising a cylindrical form of insulating material arranged to be mounted about the neck of a cathode ray tube, a pair of centering coils mounted on said form, a hollow toroidal core of magnetic material mounted about said coils, a focusing coil Within said core, and means for retaining said coils and said form and said core in xed relation to one another as a unitary assembly.

4. A combined focusing and centering coil assembly for a cathode ray tube comprising a cylindrical form of insulating material arranged to be mounted about the neck of a cathode ray tube, a pair of centering coils mounted on said form, a hollow toroidal core of magnetic material mounted about said coils, said core comprising an internal member having an outwardly extending iiange and an external member having an inwardly extending flange, a focus ,coil arranged to fit about said internal member within said core, means for locking said internal member to said external member, and means including a portion of said form for locking said centering coils in position against axial movement with respect to said core.

5. A combined focusing and centering coil assembly for a cathode ray tube comprising a cylindrical insulating form arranged to be mounted about the neck of a cathode ray tube, a pair of .centering coils mounted on said form and having axes at from each other and from the axis of said form, la 4cylindrical magnetic core surrounding said coils and having an outwardly extending flange at one end, a focusing coil mounted on said core and extending axially beyond the end remote from said ange, a second cylindrical magnetic core surrounding said focusing coil and engaging the outer portion of said flange, said second core having an inwardly extending fiange enclosing said focusing coil and providing an annular air gap between its inner edge and said other end of said rst core, said coil form having an outwardly extending lug thereon entering said air gap for preventing axial removal of said centering -coil from said core, and means for retaining said second core in engagement with' said outwardly extending flange,

DONALD R. DE TAR.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date Great Britain Jan. 12, 1938 Number Number 

